Abstract
The stability of wetlands is threatened by the combined effects of global climate change and human activity. In particular, the vegetation cover status of lake wetlands has changed. Here, the change in vegetation cover at the estuary of Poyang Lake was monitored, and its influencing factors are studied to elucidate the dynamic change characteristics of vegetation at the inlet of this lake. Flood and water level changes are two of the main factors affecting the evolution of wetland vegetation at the estuary of Poyang Lake. Therefore, Landsat data from 2000 to 2019 were used to study the spatial and temporal variation in the Normalized Difference Vegetation Index (NDVI) in the vegetation cover area. Theil–Sen Median trend analysis and Mann–Kendall tests were used to study the long-term trend characteristics of NDVI. The response between NDVI and the explanatory variables at the estuary of Poyang Lake was quantified using regression tree analysis to study the regional climate, water level, and flood inundation duration. Results showed the following: (1) Vegetation in a large area of the study area improved significantly from 2000 to 2010 and only slightly from 2010 to 2019, and few areas with slight degradation of vegetation were found. In most of these areas, the vegetation from 2000 to 2010 exhibited a gradual change, from nothing to something, which started around 2004; (2) The main variable that separated the NDVI values was the mean water level in October. When the mean October water level was greater than 14.467 m, the study area was still flooded in October. Thus, the regional value of BestNDVI was approximately 0.3, indicating poor vegetation growth. When the mean water level in October was less than 14.467 m, the elevation of the study area was higher than the water level value, and after the water receded in October, the wetland vegetation exhibited autumn growth in that year. Thus, the vegetation in the study area grew more abundantly. These results could help manage and protect the degraded wetland ecology.
Highlights
IntroductionWetlands function as ecological processes, including hydrological retention, nutrient transformation, biological survival, and growth and plant diversity [2,3,4,5]
Wetland is a transition zone located between terrestrial and aquatic ecosystems [1].Wetlands function as ecological processes, including hydrological retention, nutrient transformation, biological survival, and growth and plant diversity [2,3,4,5]
By using the regional NDVImax synthetic map from 2000 to 2019, the variation of Normalized Difference Vegetation Index (NDVI) in the study area for 20 years is clearly presented in the figure
Summary
Wetlands function as ecological processes, including hydrological retention, nutrient transformation, biological survival, and growth and plant diversity [2,3,4,5]. Wetlands have three important structural parameters: saturated soils, plant community composition, and hydrological characteristics [7]. Different combinations of hydrological characteristics and vegetation create a rich variety of wetland types. The types of this ecosystem include coastal wetlands, inland wetlands, and artificial wetlands. Lake wetlands develop from the cold temperate zone to the tropics, from plains to mountains and plateaus, and from coastal to inland regions [6,8,9,10,11]. Wetland conservation research focuses on two aspects: the interpretation of soil structure and vegetation patterns from a. Information of Poyang Lake and Yangtze Finless Porpoises.
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